{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/127462"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/127462","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Transient thermal phenomena in phase change material integrated electronics cooling","abstract":"Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2026-12-01","abstract_html":"Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2026-12-01","abstract_has_math":false,"creators":["Kim, Soonwook"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Mechanical Engineering","degree_department":null,"school":null,"contributors":["King, William P","Miljkovic, Nenad","Stillwell, Andrew","Cai, Lili"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2024,"date_issued":"2024-11-22","date_published":"2024-11-22","updated_at":"2026-07-22T22:25:04Z","subjects":["Electronics Cooling","Phase Change Material","Transient Thermal Management"],"languages":["en","eng"],"rights":["Copyright 2024 Soonwook Kim"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/2142/127462","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["King, William P","Miljkovic, Nenad","Stillwell, Andrew","Cai, Lili"]},{"key":"dc:creator","label":"Author","values":["Kim, Soonwook"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2024-11-22","2024-12"]},{"key":"dc:type","label":"Dc Type","values":["text","Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Mechanical Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Electronics Cooling","Phase Change Material","Transient Thermal Management"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en","eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2024 Soonwook Kim"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://hdl.handle.net/2142/127462"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2026-12-01","The student, Soonwook Kim, accepted the attached license on 2024-11-19 at 08:06.","The student, Soonwook Kim, submitted this Dissertation for approval on 2024-11-19 at 08:09.","This Dissertation was approved for publication on 2024-11-22 at 09:51.","DSpace SAF Submission Ingestion Package generated from Vireo submission #21339 on 2025-03-28 at 14:54:57","The growing demands of electrification and continuous miniaturization of devices pose significant challenges for the thermal management of modern power electronics. Phase change materials (PCMs) represent an opportunity for efficient cooling of devices undergoing cyclic thermal loads due to their high thermal capacitance arising from their large latent heats of phase transition. However, their narrow operational range and low thermal conductivity limit their performance and applicability in practical settings. Therefore, it is important to explore strategies for enhancing PCM thermal properties and identifying optimal operating conditions to maximize the effectiveness of PCM-integrated cooling. This dissertation examines the effectiveness of PCM cooling in managing transient thermal loads in electronic systems, with applications ranging from single-chip devices to multichip system, and further to liquid cooling configuration. The study begins by analyzing the influence of diverse pulse train heat load conditions on the cooling performance of Field’s metal/Cu foam composite PCM-integrated gallium nitride device (GaN), represented by the junction temperature swing. Reduced-order model (ROM) is developed to efficiently predict thermal performance, achieving up to 4000X faster calculation speed compared with finite element simulations with good fidelity. Next, the work reports computationally efficient design optimization strategy for PCM heat sinks using a Gaussian process (GP) optimization coupled with ROM, which produces optimization times up to 39X faster than particle swarm optimization. The work further extends this methodology to optimize GaN device reliability under transient heat loads, assessing the impact of various transient conditions and PCM selections on optimization outcomes. The dissertation also explores the application of dynamic phase change material (dynPCM) in electronics transient cooling, which uses pressure-enhanced close-contact melting to provide non-degrading cooling. The work investigates the effectiveness of the dynPCM integration on electronics with discrete heat sources, featuring both homogeneous and heterogeneous heat loads across multiple devices. DynPCM demonstrates superior transient cooling by maintaining thin melt layers and reducing thermal resistance, outperforming conventional cooling systems in managing high heat fluxes, with over a 50% reduction in junction temperature observed at heat fluxes higher than 32.4 W/cm². The work further reports on the integration of dynPCM with liquid cooling systems, illustrating how the combined approach can potentially downsize the system while maintaining cooling efficiency. Experimental results show that the combination of dynPCM and the liquid cooled cold plate can achieve the same cooling power as the liquid cooled cold plate alone at a much lower cold plate coolant flow rate and pressure drop, achieving up to 52% lower flow rate to maintain a similar heat source temperature, corresponding to a 71% reduction in pressure drop. FEM simulations predict further performance improvements in operating conditions beyond the measured cases. The findings of this dissertation demonstrate the advantages of PCM- and dynPCM-integrated systems in addressing peak thermal loads, enhancing device reliability, and enabling more compact cooling designs. The methodologies and insights presented in this dissertation provide a pathway for developing advanced thermal management solutions that meet the demands of modern high-power electronic devices."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Transient thermal phenomena in phase change material integrated electronics cooling"]}]}],"canonical_facts":{"dc:contributor":["King, William P","Miljkovic, Nenad","Stillwell, Andrew","Cai, Lili"],"dc:creator":["Kim, Soonwook"],"dc:date":["2024-11-22","2024-12"],"dc:description":["Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2026-12-01","The student, Soonwook Kim, accepted the attached license on 2024-11-19 at 08:06.","The student, Soonwook Kim, submitted this Dissertation for approval on 2024-11-19 at 08:09.","This Dissertation was approved for publication on 2024-11-22 at 09:51.","DSpace SAF Submission Ingestion Package generated from Vireo submission #21339 on 2025-03-28 at 14:54:57","The growing demands of electrification and continuous miniaturization of devices pose significant challenges for the thermal management of modern power electronics. Phase change materials (PCMs) represent an opportunity for efficient cooling of devices undergoing cyclic thermal loads due to their high thermal capacitance arising from their large latent heats of phase transition. However, their narrow operational range and low thermal conductivity limit their performance and applicability in practical settings. Therefore, it is important to explore strategies for enhancing PCM thermal properties and identifying optimal operating conditions to maximize the effectiveness of PCM-integrated cooling. This dissertation examines the effectiveness of PCM cooling in managing transient thermal loads in electronic systems, with applications ranging from single-chip devices to multichip system, and further to liquid cooling configuration. The study begins by analyzing the influence of diverse pulse train heat load conditions on the cooling performance of Field’s metal/Cu foam composite PCM-integrated gallium nitride device (GaN), represented by the junction temperature swing. Reduced-order model (ROM) is developed to efficiently predict thermal performance, achieving up to 4000X faster calculation speed compared with finite element simulations with good fidelity. Next, the work reports computationally efficient design optimization strategy for PCM heat sinks using a Gaussian process (GP) optimization coupled with ROM, which produces optimization times up to 39X faster than particle swarm optimization. The work further extends this methodology to optimize GaN device reliability under transient heat loads, assessing the impact of various transient conditions and PCM selections on optimization outcomes. The dissertation also explores the application of dynamic phase change material (dynPCM) in electronics transient cooling, which uses pressure-enhanced close-contact melting to provide non-degrading cooling. The work investigates the effectiveness of the dynPCM integration on electronics with discrete heat sources, featuring both homogeneous and heterogeneous heat loads across multiple devices. DynPCM demonstrates superior transient cooling by maintaining thin melt layers and reducing thermal resistance, outperforming conventional cooling systems in managing high heat fluxes, with over a 50% reduction in junction temperature observed at heat fluxes higher than 32.4 W/cm². The work further reports on the integration of dynPCM with liquid cooling systems, illustrating how the combined approach can potentially downsize the system while maintaining cooling efficiency. Experimental results show that the combination of dynPCM and the liquid cooled cold plate can achieve the same cooling power as the liquid cooled cold plate alone at a much lower cold plate coolant flow rate and pressure drop, achieving up to 52% lower flow rate to maintain a similar heat source temperature, corresponding to a 71% reduction in pressure drop. FEM simulations predict further performance improvements in operating conditions beyond the measured cases. The findings of this dissertation demonstrate the advantages of PCM- and dynPCM-integrated systems in addressing peak thermal loads, enhancing device reliability, and enabling more compact cooling designs. The methodologies and insights presented in this dissertation provide a pathway for developing advanced thermal management solutions that meet the demands of modern high-power electronic devices."],"dc:format":["application/pdf"],"dc:identifier":["https://hdl.handle.net/2142/127462"],"dc:language":["en","eng"],"dc:rights":["Copyright 2024 Soonwook Kim"],"dc:subject":["Electronics Cooling","Phase Change Material","Transient Thermal Management"],"dc:title":["Transient thermal phenomena in phase change material integrated electronics cooling"],"dc:type":["text","Thesis"],"thesis:degree_discipline":["Mechanical Engineering"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:25:04Z"}